Scientists find evidence of Martian lake

A US spacecraft orbiting Mars has provided evidence of an ancient crater lake fed by groundwater, adding further support to theories that the Red Planet may once have hosted life, NASA says.

Spectrometer data from NASA's Mars Reconnaissance Orbiter (MRO) shows traces of carbonate and clay minerals usually formed in the presence of water at the bottom of the 2.2km-deep McLaughlin Crater.

"These new observations suggest the formation of the carbonates and clay in a groundwater-fed lake within the closed basin of the crater," NASA said of the findings, which were published in the online edition of Nature Geoscience.

"Some researchers propose the crater interior catching the water," the space agency said, adding: "The underground zone contributing the water could have been wet environments and potential habitats."

The crater lacks large inflow channels, so the lake was likely fed by groundwater, scientists said.

The latest observations "provide the best evidence for carbonate forming within a lake environment instead of being washed into a crater from outside," said Joseph Michalski, lead author of the paper.

The 91km-wide crater sits at the low end of a regional slope several hundreds of kilometres long and, as on Earth, groundwater-fed lakes would be expected to occur at low elevations.

NASA's Mars rover Curiosity has been exploring the planet's surface since its dramatic landing on August 6, collecting rock samples and beaming back rare images in anticipation of an eventual manned mission.

MRO scientist Rich Zurek, of NASA's Jet Propulsion Laboratory, said the latest findings indicate "a more complex Mars than previously appreciated, with at least some areas more likely to reveal signs of ancient life than others".